ARENBERG, France -- Dutch rider Lars Boom won a chaotic, crash-marred fifth stage of the Tour de France on Wednesday marked by the withdrawal of defending champion Chris Froome after his second fall in two days.

Riders became wary of the stage full of cobblestone sections when the route was revealed last October, and their fears worsened when rain slicked the already treacherous path from Ypres, Belgium, to Arenberg-Porte du Hainaut.

Sensing the danger, race organizers scrapped two of the nine scheduled cobblestone patches, and reduced the stage by three kilometers (two miles). But that still wasn't enough to stop many riders from tumbling.

Froome, already nursing pain in his left wrist from a crash on Tuesday, took a spill even before the cobblestones halfway through the stage. With a cut under his right eye, the Team Sky leader limped over to a team car, climbed in, and quit a three-week race that became wide open.

The team wrote on Twitter: "Heartbreak for Chris Froome after another hard crash."

Race leader Vincenzo Nibali was one of several high-profile riders who crashed, recovered and excelled on the 152.5-kilometer (95-mile) route. The Italian finished third and extended his lead. He and second-place Jakob Fuglsang of Denmark were 19 seconds behind Boom.

"This is a special, special day for me," said Boom, who rides for Belkin Pro Cycling. "I was really looking forward to the cobblestones."

Others who went down but kept going included Americans Andrew Talansky and Tejay van Garderen, Jurgen van den Broeck of Belgium, and Alejandro Valverde of Spain. Marcel Kittel, winner of three of the race's first four stages, crashed too, but recovered.

While the chaos on the course raised questions about riding in such poor conditions -- and critics in social media had a field day -- it made for great racing imagery: Many riders were caked in sloppy wet mud on their faces and shins, their biceps jiggling as they held their handlebars. A mix of sweat, rain, mud and drool dropped from many chins. Many looked as if they'd ridden through a shower of chocolate pudding.

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